Whitney Thornton pauses on her walk along the Bayview Marsh behind Bayview Avenue to peer into a small, plastic cage protecting young wetland plants from the elements. From the shoreline, the cages, planted at seemingly random spots in the shallow water, look like traps for catching fish, clams, or perhaps crabs. But Thornton isn’t looking for dinner. Instead, this marine biologist is developing new methods of restoring wetlands damaged by invasive Spartina, or cordgrass.